Silica particles surface-treated with silane, process for producing the same and uses thereof

ABSTRACT

Fine silica particles surface-treated with a silane and having primary particles having a particle diameter of from 0.01 to 5 μm, which fine silica particles fulfill the following conditions (i) and (ii), a process for their production and an organic resin composition containing such particles as a component are provided. (i) When an organic compound which is liquid at room temperature and has a dielectric constant of from 1 to 40 F/m and fine silica particles are mixed in a weight ratio of 5:1 and shaked, the fine silica particles disperse uniformly in the organic compound, and (ii) the quantity of primary particles remaining as primary particles when methanol is evaporated under heating by means of an evaporator from a dispersion prepared by dispersing the fine silica particles in methanol and thereafter the particles are held at a temperature of 100° C. for 2 hours, is in a percentage of at least 20% based on the quantity of primary particles originally present. The present fine silica particles are highly dispersible and low aggregative, and the organic resin composition containing them is useful for obtaining films having a good transparency and superior blocking resistance, slip properties and scratch resistance.

This application is a Divisional Application of U.S. Ser. No.09/312,054, filed on May 17, 1999, now U.S. Pat. No. 6,521,290.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a fine silica particles treated with a silane,and more particularly to a fine silica particles having a highdispersibility and low aggregative properties, a process for theirproduction, and an organic resin composition containing such fine silicaparticles.

2. Description of the Prior Art

As methods for the surface treatment of silica with silane, commonlyavailable methods are those in which silane is made to adhere to silicaparticle surfaces by treatment with silicone oil and those in whichsilane is chemically bonded to silica particle surfaces by treatmentwith hexamethydisilazane.

Properties required in organic resins, in particular, organic resinfilms, include transparency, blocking resistance, slip properties,scratch resistance and so forth. Adding spherical fine silica particlesin organic resin films is proposed and is reported to bring about animprovement in transparency of the resultant film (JapanesePre-examination Patent Publication (Kokai) No. 4-348147).

The silica obtained by such surface treatment can be made hydrophobicappropriately, but reactive groups such as silanol groups or alkoxylgroups remaining on the silica particle surfaces may make the silicaunable to be dispersed in organic solvents of various types, or may makeit highly aggregative. Accordingly, it has been sought to provide finesilica particles having a high dispersibility and low aggregativeproperties.

Japanese Pre-examination Patent Publication (Kokai) No. 2-160613discloses fine silica particles having a superior dispersibility, which,however, have a problem that any heating for evaporating solvents mayresult in a poor primary-particle retention.

When the spherical fine silica particles disclosed in JapanesePre-examination Patent Publication (Kokai) No. 4-348147 are compoundedas a component of a heat-curable or ultra-violet-curable resincomposition which is liquid in a relatively low viscosity, the finesilica particles can be dispersed with difficulty in various resins andsolvents because they are inorganic matter and hence have so large aspecific gravity (larger than 2.0) that they may have a great differencein specific gravity from other materials (components) of thecomposition, and also because the fine silica particles tend toaggregate on account of the polarity or hydrogen bond of the silanolgroups they have. Thus, they have a disadvantage of sedimentation withtime during the storage of the composition.

SUMMARY OF THE INVENTION

Accordingly, an object of the present invention is to provide finesilica particles having a high dispersibility and low aggregativeproperties, and a process for their production.

Another object of the present invention is to provide an organic resincomposition which is an organic resin composition which contain finesilica particles having a high dispersibility and a high stability withtime, and hence can form a film having a good transparency and superiorblocking resistance, slip properties and scratch resistance.

The present invention provides silane-surface-treated fine silicaparticles having primary particles having a particle diameter of from0.01 to 5 μm, which fine silica particles fulfill the followingconditions (i) and (ii).

-   (i) When an organic compound which is liquid at room temperature and    has a dielectric constant of from 1 to 40 F/m and fine silica    particles are mixed in a weight ratio of 5:1 and shaken, the fine    silica particles disperse uniformly in the organic compound.-   (ii) The quantity of primary particles remaining as primary    particles when methanol is evaporated under heating by means of an    evaporator from a dispersion prepared by dispersing the fine silica    particles in methanol and thereafter the particles are held at a    temperature of 100° C. for 2 hours, is in a percentage of at least    20% based on the quantity of primary particles originally present.

As a process for producing the above silane-surface-treated fine silicaparticles, the present invention also provides a process for producingsilane-surface-treated fine silica particles, comprising the steps of:

(A) introducing an R²SiO_(3/2) unit (wherein R² represents a substitutedor unsubstituted monovalent hydrocarbon group having 1 to 20 carbonatoms) to the surfaces of hydrophilic fine silica particles comprisingan SiO₂ unit to obtain hydrophobic fine silica particles; and

(B) introducing an R¹ ₃SiO_(1/2) unit (wherein R¹'s may be the same ordifferent and each represent a substituted or unsubstituted monovalenthydrocarbon group having 1 to 6 carbon atoms) to the surfaces of theresultant hydrophobic fine silica particles.

This process can provide highly dispersible and low aggregativehydrophobic fine silica particles having a particle diameter of from0.01 to 5 μm.

The present invention further provides an organic resin film comprising(a) 100 parts by weight of an organic resin and (b) from 0.01 to 10parts by weight of the above silane-surface-treated fine silicaparticles.

The silane-surface-treated fine silica particles obtained by the presentinvention have a high dispersibility and low aggregative properties anyconventional ones do not have. The present fine silica particles canpreferably be used to modify properties (slip properties, wearresistance, lubricity, and anti-blocking flexibility) of various rubbersand synthetic resins, to improve properties of coating materials and inkcoating agents and to impart lubricating properties and water repellencyto cosmetics, and also as a fluidity-providing agent for various powderssuch as abrasive particles for abrasives, and powdery resins.

In particular, the organic resin composition of the present invention isformed using the above highly dispersible fine silica particles as amaterial, and may hardly cause the settlement of fine silica particleseven with time. Hence, it can form a film having a good transparency andsuperior blocking resistance, slip properties and scratch resistance.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention will be described below in detail.

A process for producing the fine silica particles of the presentinvention will be described in the order of steps.

Step (A)

In the process of the present invention, there are no particularlimitations on hydrophilic fine silica particles used in the step (A) asa starting material. They may include, e.g., those obtained by a processcomprising the step of subjecting a tetrafunctional silane compoundrepresented by the general formula (I):Si(OR³)₄  (I)(wherein R³'s may be the same or different and each represent amonovalent hydrocarbon group having 1 to 6 carbon atoms) or a partialhydrolysis-condensation product thereof or a mixture of these, tohydrolysis and condensation in a mixed solvent of water and ahydrophilic organic solvent containing a basic substance, to obtain ahydrophilic fine silica particle mixed-solvent dispersion, andsubsequently the step of converting the dispersion medium of thehydrophilic fine silica particle mixed-solvent dispersion into water toprepare an aqueous hydrophilic fine silica particle dispersion.

As specific examples of the tetrafunctional silane compound representedby the general formula (I), it may include tetraalkoxysilanes such astetramethoxysilane, tetraethoxysilane, tetraisopropoxysilane andtetrabutoxysilane. As specific examples of the partialhydrolysis-condensation product of the tetrafunctional silane compoundrepresented by the general formula (I), it may include methyl silicateand ethyl silicate. Any of these may be used alone or in combination oftwo or more.

There are no particular limitations on the hydrophilic organic solventso long as it dissolves the compound of the general formula (I) orpartial hydrolysis-condensation product and the water. It may includealcohols, cellosolves such as methyl cellosolve, ethyl cellosolve, butylcellosolve and cellosolve acetate, ketones such as acetone and methylethyl ketone, and ethers such as dioxane and tetrahydrofuran. Preferredare alcohols. The alcohols may include alcohol solvents represented bythe general formula (V):R⁶OH  (V)(wherein R⁶ represents a monovalent hydrocarbon group having 1 to 6carbon atoms). As specific examples, such alcohols may include methanol,ethanol, isopropanol and butanol. The particle diameter of fine silicaparticles formed increases with an increase in the number of carbonatoms of alcohols, and hence it is desirable to select the type ofalcohols in accordance with the intended particle diameter of finesilica particles.

The above basic substance may include ammonia, dimethylamine anddiethylamine. Any of these basic substances may be dissolved in water ina necessary quantity and thereafter the resultant aqueous solution(basic water) may be mixed with the hydrophilic organic solvent.

The water used here may preferably be in an amount of from 0.5 to 5equivalent weight per mole of the silane compound of the general formula(I) or its partial hydrolysis-condensation product. The water and thehydrophilic organic solvent may preferably be in a ratio of from 0.5 to10 in weight ratio. The basic substance may preferably be in an amountof from 0.01 to 1 equivalent weight per mole of the silane compound ofthe general formula (I) or its partial hydrolysis-condensation product.

The hydrolysis and condensation of the tetrafunctional silane compoundof the general formula (I) is carried out by a known process in whichthe tetrafunctional silane compound of the general formula (I) is addeddropwise in a mixture of the water and the hydrophilic organic solventcontaining a basic substance. The dispersion medium of the hydrophilicfine silica particle mixed-solvent dispersion may be converted intowater by, e.g., a process of adding water to the dispersion andevaporating the hydrophilic organic solvent (this process may optionallybe repeated). The water added here may preferably be used in a 0.5-foldto 2-fold amount, and preferably about 1-fold amount, in weight ratiobased on the total weight of the hydrophilic organic solvent used andalcohol formed.

The hydrophilic fine silica particles used as a starting material in thestep (A) may be the mixed solvent dispersion containing hydrophilic finesilica particles, or may be an aqueous dispersion containing hydrophilicfine silica particles because the remaining alkoxyl groups arecompletely hydrolyzed by adding water in the hydrophilic fine silicaparticle mixed-solvent dispersion and evaporating the hydrophilicorganic solvent to convert the dispersion medium of the dispersion intoan aqueous dispersion.

Stated more specifically, the step (A) comprises, e.g., adding to anaqueous dispersion or mixed-solvent dispersion containing thehydrophilic fine silica particles a trifunctional silane compoundrepresented by the general formula (II):R²Si(OR⁴)₃  (II)(wherein R² represents a substituted or unsubstituted monovalenthydrocarbon group having 1 to 20 carbon atoms, and R⁴'s may be the sameor different and each represent a monovalent hydrocarbon group having 1to 6 carbon atoms) or a partial hydrolysis-condensation product thereofor a mixture of these, to treat the surfaces of the hydrophilic finesilica particles with it to obtain an aqueous hydrophobic fine silicaparticle dispersion.

As specific examples of the trifunctional silane compound represented bythe general formula (II), it may include trialkoxysilanes such asmethyltrimethoxysilane, methyltriethoxysilane, ethyltrimethoxysilane,ethyltriethoxysilane, n-propyltrimethoxysilane, n-propyltriethoxysilane,i-propyltrimethoxysilane, i-propyltriethoxysilane,butyltrimethoxysilane, butyltriethoxysilane, hexyltrimethoxysilane,trifluoropropyltrimethoxysilane andheptadecafluorodecyltrimethoxysilane. Partial hydrolysis-condensationproducts of these may also be used. Any of these may be used alone or incombination of two or more.

The trifunctional silane compound represented by the general formula(II) may be added in an amount of from 1 to 0.001 equivalent weight, andpreferably from 0.1 to 0.01 equivalent weight, per mole of the SiO₂ unitof the hydrophilic fine silica particles used.

Step (B)

Stated more specifically, the step (B) comprises, e.g., the step ofconverting the dispersion medium of the aqueous hydrophobic fine silicaparticle dispersion into a ketone solvent from the water or hydrophilicorganic solvent and the alcohol mixture to obtain a hydrophobic finesilica particle ketone solvent dispersion, and the step of adding to thehydrophobic fine silica particle ketone solvent dispersion amonofunctional silazane compound represented by the general formula(III):R¹ ₃SiNHSiR¹ ₃  (III)(wherein R¹'s may be the same or different and each represent asubstituted or unsubstituted monovalent hydrocarbon group having 1 to 6carbon atoms), a monofunctional silane compound represented by thegeneral formula (IV):R¹ ₃SiX  (IV)(wherein R¹'s are as defined in the general formula (III), and Xrepresents a hydroxyl group or a hydrolyzable group) or a mixture ofthese to make triorganosilylation of reactive groups remaining on thesurfaces of the hydrophobic fine silica particles.

The dispersion medium of the aqueous fine silica particle dispersion ormixed-solvent dispersion may be converted into a ketone solvent from thewater or hydrophilic organic solvent and the alcohol mixture, by aprocess of adding a ketone solvent to the dispersion and evaporating thewater or hydrophilic organic solvent and the alcohol mixture (thisprocess may optionally be repeated). The ketone solvent added here maypreferably be used in a 0.5-fold to 5-fold amount, and preferably about1- to 2-fold amount, in weight ratio based on the weight of thehydrophilic fine silica particles used. As specific example of theketone solvent used here, it may include methyl ethyl ketone, methylisobutyl ketone and acetyl acetone. Preferred is methyl ethyl ketone.

As specific examples of the silazane compound represented by the generalformula (III), it may include hexamethyldisilazane. As specific examplesof the monofunctional silane compound represented by the general formula(IV), it may include monosilanol compounds such as trimethylsilanol andtriethylsilanol, monochlorosilanes such as trimethylchlorosilane andtriethylchlorosilane, monoalkoxysilanes such as trimethylmethoxysilaneand trimethylethoxysilane, monoaminosilanes such astrimethylsilyldimethylamine and trimethylsilyldiethylamine andmonoacyloxysilanes such as trimethylacetoxysilane. Any of these may beused alone or in combination of two or more.

These may each be used in an amount of from 0.1 to 0.5 equivalentweight, and preferably from 0.2 to 0.3 equivalent weight, per mole ofthe SiO₂ unit of the hydrophilic fine silica particles used.

Thus, the highly dispersible and low aggregative fine silica particleshaving a particle diameter of from 0.01 to 5 μm, and preferably from0.01 to 1 μm can be obtained in which the fine silica particlescomprising SiO₂ units have been coated with R²SiO_(3/2) units (whereinR² is as defined in the general formula (II)) and the reactive groupsremaining on the surfaces of these particles have been blocked with R¹₃SiO_(1/2) units (wherein R¹'s are as defined in the general formula(III)).

Such fine silica particles may be taken out as a powder by aconventional method, or may be obtained as a dispersion thereof to whichan organic compound has been added after the reaction with silazane.

Organic Resin Composition

The organic resin composition of the present invention consistsbasically of (a) an organic resin and (b) the silane-surface-treatedfine silica particles described above.

The component-(a) organic resin used in the organic resin composition ofthe present invention may be either of a thermoplastic resin and acurable resin.

The thermoplastic resin may include, e.g., polyolefins such aspolypropylene and polyethylene, polyesters such as polyethyleneterephthalate and polybutylene terephthalate, and polyamides such asnylon 6 and nylon 66.

The composition comprising the curable resin may include, e.g.,heat-curable resin compositions such as an epoxy resin composition andan unsaturated polyester resin composition, and ultraviolet-curableresin compositions such as an epoxy acrylate resin composition and aurethane acrylate resin composition.

The component-(b) silane-surface-treated fine silica particles have beenmade highly hydrophobic, and hence are readily dispersible in variousorganic solvents and organic resins. Also, the silanols groups, whichadversely affect the slip properties and blocking resistance of theresin film surface, are almost not present on the particle surfaces, andhence this brings about good results on the object and effect of thepresent invention. The present fine silica particles may preferably havea particle diameter of from 0.01 to 5 μm, and more preferably from 0.05to 1 μm, in view of good slip properties and blocking resistance of theresin film surface and good transparency and also in view of theadvantage that the particles may hardly settle even with time in theuncured resin composition.

Usually, the component-(b) fine silica particles may preferably becompounded in an amount of from 0.01 to 10 parts by weight, and morepreferably from 0.1 to 5 parts by weight, based on 100 parts by weightof the organic resin. It is easy for those who skilled in the art todetermine more preferable amount within such a range in accordance withthe types of resins. Its compounding in a too small amount commonlytends to make it less effective to improve the slip properties andblocking resistance of the film, and its compounding in a too largeamount tends to make the resultant resin film have a low transparencyand a low strength.

In addition to the components (a) and (b) described above, stabilizerssuch as an antioxidant and a ultraviolet light absorber, a processingaid, a colorant, an antistatic agent, a lubricant and so forth mayoptionally be added and compounded in the organic resin composition ofthe present invention so long as the effect of the present invention isnot damaged

The above silane-surface-treated fine silica particles may be compoundedin the organic resin by a known method, and a mixing machine such as aHenschel mixer, a V-type blender, a ribbon blender or an automaticmortar may be used. In the case when the composition has a lowviscosity, the respective components in prescribed quantities mayuniformly be mixed by means of a kneader mixer, a butterfly mixer or ausual mixing machine having a propeller stirrer. Thus, the organic resincomposition of the present invention can be obtained.

Films may be formed from this composition by a known method, includingT-die extrusion, circular die extrusion or biaxial orientation. In thecase when the composition has a low viscosity, films may be formed bytransferring or coating followed by hardening.

Other Uses

The silane-surface-treated fine silica particles of the presentinvention are also useful as an additive when polyurethane foams areproduced. More specifically, the silane-surface-treated fine silicaparticles described above are previously added to a resin mix whenpolyurethane foams are produced by expanding and curing a polyurethanefoam composition containing i) a resin premix containing a polyol, wateras a blowing agent, a catalyst and a surface-active agent as a foamstabilizer and ii) a polyisocyanate. The silane-surface-treated finesilica particles may preferably have a particle diameter of from 0.1 to1 μm, and may usually be added in a 0.01-fold to 20-fold amount,preferably a 0.5-fold amount, in weight ratio to the polyol. The finesilica particles of the present invention do not separate or deterioratein the resin premix, and the resin premix can stably be stored for along term. Thus, the resin premix need not be agitated when used, andalso can be free from any damage of the desired properties such asdimensional stability. In addition, it has an advantage that it can alsobe used in spray blowing.

The silane-surface-treated fine silica particles of the presentinvention are also useful as a modifying agent of printing paper.Cellulose fibers constituting a paper base may be covered with thesilane-surface-treated fine silica particles of the present invention atleast partly. The printing paper thus obtained can have superior printedimages, water resistance and moisture resistance. Accordingly,especially when printed using printers such as ink-jet printers andlaser printers, it is unnecessary to provide any flat ink-receivinglayer specially as in the paper exclusively used for such printers or touse thick paper in order to improve deformation resistance at the timeof high-temperature fixing. Thus, the printing paper can be used likeplain paper. To obtain such paper modified with the fine silicaparticles of the present invention, paper may be made from a dispersioncontaining cellulose fibers and the fine silica particles of the presentinvention, or the paper base may be coated or impregnated with such adispersion. In this instance, the fine silica particles may preferablyhave an average particle diameter of from 0.01 to 0.5 μm.

EXAMPLES

The present invention will be described below in greater detail bygiving Examples and Comparative Examples.

Example 1

(1) In a 3-liter glass reaction vessel having a stirrer, a droppingfunnel and a thermometer, 623.7 g of methanol, 41.4 g of water and 49.8g of 28% ammonia water were added and then mixed. The resultant solutionwas kept at 35° C., and 1,163.7 g of tetramethoxysilane and 418.1 g of5.4% ammonia water were begun being simultaneously added thereto whilestirring the solution, where the former and the latter were addeddropwise in 6 hours and 4 hours, respectively. After thetetramethoxysilane had been added dropwise, too, the solution wascontinued being stirred for 0.5 hour to carry out hydrolysis, thus asuspension of fine silica particles was obtained. An ester adapter and acooling pipe were attached to the glass reaction vessel, and thedispersion was heated to 60 to 70° C. to evaporate 649 g of methanol,where 1,600 g of water was added, followed by further heating to 70 to90° C. to evaporate 160 g of methanol, thus an aqueous suspension offine silica particles was obtained.

(2) To this aqueous suspension, 115.8 g of methyltrimethoxysilane (0.1equivalent weight per mole of tetramethoxysilane) and 46.6 g of 5.4%ammonia water were added dropwise at room temperature in 0.5 hour. Afterthey had been added dropwise, too, the dispersion was stirred for 12hours to treat the fine silica particle surfaces.

(3) To the dispersion thus obtained, 1,000 g of methyl isobutyl ketonewas added, followed by heating to 80 to 110° C. to evaporate 1,336 g ofmethanol water in 11 hours. To the resultant dispersion, 357.6 g ofhexamethyldisilazane was added at room temperature, which was thenheated to 120° C. to carry out reaction for 3 hours to effecttrimethylsilylation of the fine silica particles. Thereafter, thesolvent was evaporated under reduced pressure to obtain 477 g ofsilane-surface-treated fine silica particles

The silane-surface-treated fine silica particles thus obtained weretested in the following way.

Dispersibility Test:

The fine silica particles are added to an organic compound which isliquid at room temperature, in a weight ratio of 5:1, which are thenshaken for 30 minutes by means of a shaker to mix them, and thereafterthe state of dispersion is visually observed. An instance where the finesilica particles stand dispersed in their entirety and the whole isuniformly in the state of a slurry is evaluated as “∘”; an instancewhere the fine silica p articles stand wetted with the organic compoundin their entirety, but not dispersed in the oragnic compound partly andnon-uniform, as “Δ”; and an instance where the fine silica particlesstand not wetted with the organic compound and the both do not mix, as“x”. The results are shown in Table 3.

Aggregation Accelerating Test:

(1) The fine silica particles are added to methanol in a weight ratio of5:1, which are then shaken for 30 minutes by means of a shaker. Particlesize distribution of the fine silica particles thus treated is measuredwith a laser diffraction scattering type particle size distributionanalyzer (LA910, manufactured by Horiba Seisakusho).

(2) Next, from the fine-particle dispersion obtained in (1), themethanol is evaporated under heating, by means of an evaporator, and theparticles are held at a temperature of 100° C. for 2 hours. The finesilica particles thus treated are added in methanol, and then shaken for30 minutes by means of a shaker. Thereafter, their particle sizedistribution is measured in the same manner as the above.

Percentage of particles remaining as primary particles is determined onthe basis of the particle size distribution measured in (1). Primaryparticle diameter is beforehand ascertained by electron-microscopicobservation. The results are shown in Table 3.

Silicone Viscosity Test:

Viscosity of a sample obtained by adding and dispersing 10 g of finesilica particles in 190 g of dimethylsilicone oil (viscosity: 1,000cSt/25° C.) is measured with a BM-type rotational viscometer. Theviscosity is measured at a rotational speed of 60 rpm. The results areshown in Table 3.

Fluidity Test:

To 100 g of a pulverized product (particle diameter: 5 to 20 μm) of astyrene-acrylate 70:30 copolymer having a melting point of 120° C., 1 gof fine silica particles are added to examine the fluidity of thecopolymer pulverized product. The results are shown in Table 3.

Examples 2 to 7

Silane-surface-treated fine silica particles were obtained in the samemanner as in Example 1 except that the hydrolysis temperature, theamount of water added, the manner of adding 5.4% ammonia water dropwiseand its amount, the manner of adding methyltrimethoxysilane dropwise andits amount and the amount of methyl isobutyl ketone were changed asshown in Table 1. In Example 5, the evaporation of methanol was notoperated.

The fine silica particles thus obtained were tested in the same manneras in Example 1. The results are shown in Table 3.

Comparative Example 1

Hydrophobic fine silica particles were tried being produced in the samemanner as in Example 1 except that the step of treating fine silicaparticles with methyltrimethoxysilane and 5.4% ammonia water wasomitted. As a result, the dispersion of fine silica particles solidifiedat the time of the evaporation of water.

Comparative Example 2

Silane-surface-treated fine silica particles were obtained in the samemanner as in Example 1 except that the step of trimethylsilylation offine silica particles with use of hexamethyldisilazane was omitted.

Comparative Example 3

Silane-surface-treated fine silica particles were obtained in the samemanner as in Example 1 except that the water used therein was replacedwith a mixture comprised of 1,000 parts by weight of water and 1,000parts by weight of methyl isobutyl ketone.

Using the silane-surface-treated fine silica particles obtained inComparative Examples 2 and 3, the dispersibility test, aggregationaccelerating test, silicone viscosity test and fluidity test were madein the same manner as in Example 1 to obtain the results as shown inTable 4.

Comparative Examples 4 to 7

Using commercially available silane-surface-treated fine silicaparticles, the tests were made in the same manner as in Example 1 toobtain the results as shown in Table 4.

TABLE 1 Example 1 2 3 4 5 6 7 Hydrolysis 35 35 35 35 35 20 45temperature (° C.) Amount of water added 1600 1600 1200 1200 0 1200 1200Trimethylsilane 5.4% Ammonia reaction water: conditions: Manner ofSimul- Pre- addition taneous addition Amount 46.6 none 46.6 none nonenone none Methyltrime- thoxysilane: Manner of Simul- Simul- Post- Post-Post- Post- Post- addition taneous taneous addition addition additionaddition addition Amount 8 115.8 8 11.6 11.6 11.6 11.6 Equivalent 0.10.1 0.1 0.01 0.01 0.01 0.01 weight per mole of tetrame- thoxysilaneAmount of methyl 1444 1600 1600 1444 1444 1444 1444 isobutyl ketoneSilica particle 87 88 124 115 226 339 13 diameter (nm)

TABLE 2 Comparative Example 2 3 Silica particle diameter (nm) 273 197

TABLE 3 Organic Dielectric Example compound constant 1 2 3 4 5 6 7Dispersibility Acetonitrile 38 ◯ ◯ ◯ ◯ ◯ ◯ ◯ Methanol 33 ◯ ◯ ◯ ◯ ◯ ◯ ◯Ethanol 24 ◯ ◯ ◯ ◯ ◯ ◯ ◯ MIBK 13 ◯ ◯ ◯ ◯ ◯ ◯ ◯ THF 7 ◯ ◯ ◯ ◯ ◯ ◯ ◯Dioxane 3 ◯ ◯ ◯ ◯ ◯ ◯ ◯ D₅ 2.5 ◯ ◯ ◯ ◯ ◯ ◯ ◯ Toluene 2.4 ◯ ◯ ◯ ◯ ◯ ◯ ◯Heptane 1.9 ◯ ◯ ◯ ◯ ◯ ◯ ◯ Primary particle percentage (%) 42 80 50 10025 86 57 Silicone viscosity (cP) 2140 2370 2410 2070 2250 2380 2230Fluidity good good good good good good Good Remarks: MIBK: Methylisobutyl ketone THF: Tetrahydrofuran D₅: Decamethylcyclopentasiloxane

TABLE 4 Comparative Example 4 5 6 7 Organic Dielectric NIPSIL NIPSILAEROSIL MUSIL compound constant 2 3 SS50F SS10 R972 130A DispersibilityAcetonitrile 38 X ◯ ◯ ◯ X X Methanol 33 X ◯ ◯ Δ X X Ethanol 24 X ◯ ◯ ◯ XX MIBK 13 X ◯ ◯ ◯ X X THF 7 X ◯ ◯ ◯ X X Dioxane 3 X ◯ X X X X D₅ 2.5 X ◯Δ X X X Toluene 2.4 X ◯ ◯ X X X Heptane 1.9 X ◯ ◯ ◯ X X Primary particlepercentage —  16   0 — — — (%) Silicone viscosity (cP) 4280 3240 33903370 3910 4160 Fluidity poor Poor poor poor poor Poor Remarks: NIPSILSS50F: Trade name; available from Nippon Silica Industrial Co., Ltd.;silica obtained by treating precipitated silica particle surfaces withan organosilicon compound. NIPSIL SS10: Trade name; available fromNippon Silica Industrial Co., Ltd.; silica obtained by treatingprecipitated silica particle surfaces with (CH₃)₂SiO_(2/2) units.AEROSIL R972: Trade name; available from Nippon Aerosil Co., Ltd.;silica obtained by treating fumed silica particle surfaces with(CH₃)₂SiO_(2/2) units. MUSIL 130A: Trade name; available from Shin-EtsuChemical Co., Ltd.; silica obtained by treating fumed silica particlesurfaces with CH₃SiO_(3/2) units.

Example 8

In 100 parts by weight of T-die molding polypropylene resin NOBLENFL-200 (melt flow rate: 8 g/10 min; trade name; available from MitsuiToatsu Chemicals, Inc.), 0.5 part by weight of thesilane-surface-treated fine silica particles obtained in Example 1 wascompounded and uniformly mixed. The mixture obtained was extruded at250° C. by means of a single-screw extruder of 25 mm diameter, and theextruded product was pelletized with a pelletizer. The pellets obtainedwere further T-die extrusion-molded at 250° C. by means of asingle-screw extruder of 20 mm diameter to obtain films of 0.5 mm thick.

On the films thus obtained, the following property evaluation was made.

Transparency:

Ten sheets of film are superposed, and their total light raytransmittance is measured.

Blocking Resistance:

Two sheets of film are horizontally superposed, and are held between twoglass plates on the former's top and bottom sides. A load of 100 g/cm²is applied onto the top-side glass plate, and these are left at roomtemperature for 24 hours. Thereafter, the top-side glass plate is takenaway, and the two sheets of film standing superposed are cut in a sizeof 5 cm×5 cm to prepare a sample. The two sheets of film are pulled inthe opposite directions at the superposed end of the sample. The force(g) necessary for peeling them is measured and is regarded as an indexof blocking resistance. The smaller the force necessary for peeling is,the higher the blocking resistance is.

Slip Properties:

Coefficient of dynamic friction between the film and SBR rubber surfaceis measured according to ASTM D-1894.

The results are shown in Table 5.

Examples 9 to 12

Films were obtained in the same manner as in Example 8 except that thefine silica particles used and the amount thereof were changed as shownin Table 5. Their properties were evaluated similarly. The results areshown in Table 5.

TABLE 5 Example 8 9 10 11 12 Fine Prepared Prepared Prepared PreparedPrepared silica in in in in in particles Example 1 Example 4 Example 4Example 5 Example 6 Amount 0.3 0.1 1.0 0.3 0.3 (parts by weight) Slip0.20 0.23 0.11 0.19 0.17 properties Blocking 1.5 2.0 1.1 1.6 1.4resistance (g) Trans- 88 91 82 84 86 parency

Comparative Examples 8 to 14

Films were obtained in the same manner as in Example 8 except that thefine silica particles used and the amount thereof were changed as shownin Table 6. Their properties were evaluated similarly. The results areshown in Table 6. Silicon dioxide particles used in Comparative Example14 were ADOMAFINE SO-C5 (trade name; available from Adomatech Co.;average particle diameter: 2 μm; particle size distribution: 0.1 to 5μm)

TABLE 6 Comparative Example 8 9 10 11 12 14 Fine Prepared in Prepared inPrepared in Prepared in — Silicondioxide silica Comparative ComparativeComparative Comparative particles particles Example 3 Example 4 Example5 Example 4 Amount 0.3 0.3 0.3 0.009 0 1.0 (parts by weight) Slip 0.230.34 0.36 0.38 0.41 0.16 properties Blocking 2.2 3.0 2.9 7.6 8.2 1.5resistance (g) Transparency 79 79 74 91 92 75

Examples 13 to 16

Into a reaction vessel, 150 g of polytetramethylene ether glycol havinga number-average molecular weight of 2,000 (available from MitsubishiChemical Industries Limited; trade name: PTMG-2000), 150 g ofpolytetramethylene ether glycol having a number-average molecular weightof 1,000 (available from Mitsubishi Chemical Industries Limited; tradename: PTMG-1000), 31.6 g of neopentyl glycol and 175.4 g of2,4-tolylenediisocyanate were charged, and the mixture obtained wasreacted for 6 hours while keeping its temperature at 60 to 70° C. Theisocyanated reaction mixture thus obtained was cooled to about 40° C.,followed by addition of 0.15 g of tert-butylhydroxytoluene, 0.08 g ofdibutyltin laurate and 119.3 g of 2-hydroxyethyl acrylate. Thereafter,the mixture obtained was reacted for 2 hours while keeping itstemperature at 60 to 70° C., to obtain a urethane acrylate oligomer.Then, 55 parts by weight of this urethane acrylate oligomer, 15 parts byweight of tricyclodecanedimethanol diacrylate (available from MitsubishiChemical Industries Limited; trade name: SA-1002), 10 parts by weight ofbisphenol A-EO modified diacrylate (available from Toagosei ChemicalIndustry Co., Ltd.; trade name: M-210), 10 parts by weight ofN-vinylpyrrolidone, 10 parts by weight of isopholonyl acrylate and as aphotopolymerization initiator 3 parts by weight of 1-hydroxycyclohexylphenyl ketone were mixed, thus a ultraviolet-curable urethane acrylateresin composition was prepared.

To 100 parts by weight of the ultraviolet-curable urethane acrylateresin composition thus prepared, the fine silica particles shown inTable 7 were compounded and mixed in the amount (parts by weight) shownin Table 7, and these were further kneaded twice by means of athree-roll mill so as to be uniformly mixed. The resin compositions thusobtained were each coated on a glass plate in a thickness of from 30 to50 μm, and the coating thus formed was exposed to ultraviolet rays of200 mJ/cm² (wavelength: 350 nm) to effect curing. Thus, cured films of50 μm thick were obtained. On the films thus obtained, their propertieswere evaluated in the following way.

Evaluation of Properties

Slip Properties:

Cured films are conditioned for 24 hours at 25° C. and a relativehumidity of 50%, and thereafter the coefficient of friction betweenfilms is measured according to ASTM D1894.

Blocking Resistance:

Two sheets of cured film cut in a size of 5 cm×5 cm are horizontallysuperposed, and are held between two glass plates on the former's topand bottom sides. A load of 100 g/cm² is applied onto the top-side glassplate, and these are left at room temperature or 24 hours. Thereafter,the film is detached from the glass plates. The two sheets of film arepulled in the opposite directions at the superposed end of the film at aforce of 10 g. The extent of peel or adhesion of the film is evaluatedaccording to the following criteria.

∘: Readily peelable.

x: Standing in close adhesion.

Transparency:

Cured film of 50 μm thick is prepared in the manner as described above,and its transparency is evaluated by examining whether or not the otherside is seen through the film when looked through with the naked eye.

∘: Seen through.

x: Not seen through.

Sedimentation:

The resin composition before curing is put in a glass bottle, and isleft at 40° C., for 30 days. Thereafter, the extent of sedimentation offine silica particles is observe with the naked eye.

∘: No sedimentation is seen.

x: Sedimentation is seen, and separation into two layers is also seen.

TABLE 7 Example 13 14 15 16 Fine silica particles Prepared PreparedPrepared Prepared in in in in Example 1 Example 1 Example 4 Example 4Amount (parts by 2 5 2 5 weight) Slip properties 0.23 0.14 0.19 0.11Blocking resistance ◯ ◯ ◯ ◯ (g) Transparency ◯ ◯ ◯ ◯ Sedimentation ◯ ◯ ◯◯

Comparative Examples 15 to 18

Films were obtained in the same manner as in Examples 13 to 16 exceptthat the fine silica particles used and the amount thereof were changedas shown in Table 8. Their properties were evaluated similarly. Theresults are shown in Table 8.

Silicon dioxide particles used in Comparative Example 14 were thosesurface-treated in the following way.

100 parts by weight of ADOMAFINE SO-C5 (trade name; available fromAdomatech Co.; average particle diameter: 2 μm; particle sizedistribution: 0.1 to 5 μm) and 1 part by weight of iron-exchanged waterwere mixed by means of a mixer, and then treated by heating at 60° C.for 24 hours. The mixture thus treated was cooled to room temperature,and 2 parts by weight of hexamethyldisilazane was added thereto.Thereafter, the mixture obtained was left for 24 hours at roomtemperature, which was then treated by heating at 120° C. for 24 hoursto obtain surface-treated silicon dioxide particles.

TABLE 8 Comparative Example 15 16 17 18 Fine silica Prepared in —Prepared Surface-treated particles Comparative in silicon dioxideExample 4 Example 4 particles Amount (parts by 2 0 12 2 weight) Slipproperties 0.35 5> 0.08 0.39 Blocking resistance ◯ X ◯ ◯ (g)Transparency X ◯ X ◯ Sedimentation X — ◯ X

Examples 17 to 20

To 100 parts by weight of heat-curable one-part epoxy resin (availablefrom Asahi Denka Kogyo K.K.; trade name: ADEKAOPTON KT-970; viscosity:7,300 cP/25° C.), the fine silica particles shown in Table 9 werecompounded and mixed in the amount (parts by weight) shown in Table 9,and these were further kneaded twice by means of a three-roll mill so asto be uniformly mixed. The resin compositions thus obtained were eachcoated on a 0.2 mm thick aluminum sheet and a glass plate in a thicknessof from 30 to 50 μm each, and the coatings thus formed were heated at130° C. for 2 hours. Thus, cured films formed on the aluminum sheet andglass plate were obtained. On the films thus obtained, their propertieswere evaluated in the following way.

Slip Properties:

Cured films formed on the aluminum sheet are conditioned for 24 hours at25° C. and a relative humidity of 50%, and thereafter the coefficient offriction between films is measured according to ASTM D1894.

Blocking Resistance:

Two sheets of cured film cut in a size of 5 cm×5 cm are horizontallysuperposed, and are held between two glass plates on the former's topand bottom sides. A load of 100 g/cm² is applied onto the top-side glassplate, and these are left at room temperature for 24 hours. Thereafter,the film is detached from the glass plates. The two sheets of film arepulled in the opposite directions at the superposed end of the film at aforce of 10 g. The extent of peel or adhesion of the film is evaluatedaccording to the following criteria.

∘: Readily peelable.

x: Standing in close adhesion.

Transparency:

Cured film of 200 to 300 μm thick is formed on a glass plate in the samemanner as that described above, and its transparency is evaluated byexamining whether or not the other side is seen through the film whenlooked through with the naked eye.

∘: Seen through.

x: Not seen through.

Sedimentation:

The resin composition before curing is put in a glass bottle, and isleft at 40° C. for 30 days. Thereafter, the extent of sedimentation offine silica particles is observe with the naked eye.

: No sedimentation is seen.

x: Sedimentation is seen, and separation into two layers is also seen.

The results are shown in Table 9.

TABLE 9 Example 17 18 19 20 Fine silica particles Prepared PreparedPrepared Prepared in in in in Example 1 Example 1 Example 4 Example 4Amount (parts by 0.1 0.2 0.1 0.2 weight) Slip properties 0.18 0.13 0.130.08 Blocking resistance ◯ ◯ ◯ ◯ (g) Transparency ◯ ◯ ◯ ◯ Sedimentation◯ ◯ ◯ ◯

Comparative Examples 19 to 22

Cured films were obtained in the same manner as in Examples 17 to 20except that the fine silica particles used and the amount thereof werechanged as shown in Table 10. Their properties were evaluated similarly.The results are shown in Table 10.

Silicon dioxide particles used in Comparative Example 22 were thosesurface-treated in the following way.

100 parts by weight of ADOMAFINE SO-C5 (trade name; available fromAdomatech Co.; average particle diameter: 2 μm; particle sizedistribution: 0.1 to 5 μm) and 1 part by weight of iron-exchanged waterwere mixed by means of a mixer, and then treated by heating at 60° C.for 24 hours. The mixture thus treated was cooled to room temperature,and 2 parts by weight of hexamethyldisilazane was added thereto.Thereafter, the mixture obtained was left for 24 hours at roomtemperature, which was then treated by heating at 120° C. for 24 hoursto obtain surface-treated silicon dioxide particles.

TABLE 10 Comparative Example 19 20 21 22 Fine silica Prepared in —Prepared Surface-treated particles Comparative in silicon dioxideExample 4 Example 4 particles Amount (parts by 0.1 0 0.009 0.1 weight)Slip properties 0.38 0.45 0.41 0.21 Blocking ◯ X X ◯ resistance (g)Transparency X ◯ ◯ ◯ Sedimentation X — ◯ X

1. An organic resin composition comprising; (a) 100 parts by weight ofan organic resin; and (b) from 0.01 to 10 parts by weight ofsilane-surface-treated fine silica particles wherein saidsilane-surface-treated fine silica particles comprise primary particleshaving a particle diameter of from 0.1 to 5 μm, and the finesilane-surface-treated silica particles are obtained by: (A) introducingan R²SiO_(3/2) unit to the surface of a hydrophilic fine silica particlecomprising an SiO₂ unit to form a hydrophobic fine silica particle byadding to an aqueous dispersion medium or mixed-solvent dispersionmedium comprising the hydrophilic fine silica particle, a trifunctionalsilane compound represented by formula (II):R²Si(OR⁴)₃  (II) wherein R² represents a substituted or unsubstitutedmonovalent hydrocarbon group having 1 to 20 carbon atoms, and the R⁴groups may be the same or different and may each represent a monovalenthydrocarbon group having 1 to 6 carbon atoms, or a partialhydrolysis-condensation product thereof or a mixture thereof, to treatthe surfaces of the hydrophilic fine silica particles and form anaqueous hydrophobic fine silica particle dispersion; and (B) introducingan R¹ ₃ SiO_(1/2) unit to the surface of the hydrophobic fine silicaparticle by converting the dispersion medium of the aqueous hydrophobicfine silica particle dispersion into a ketone solvent to obtain ahydrophobic fine silica particle ketone solvent dispersion, and addingto the hydrophobic fine silica particle ketone solvent dispersion amonofunctional silazane compound represented by formula (III):  R¹₃SiNHSiR¹ ₃  (III) wherein the R¹ groups may be the same or differentand each may represent a substituted or unsubstituted monovalenthydrocarbon group having 1 to 6 carbon atoms, a monofunctional silanecompound represented by formula (IV):R¹ ₃SiX  (IV) wherein the R¹ groups are as defined in formula (III), andX represents hydroxyl group or a hydrolyzable group, or a mixturethereof to triorganosilylate the reactive groups remaining on thesurface of the hydrophobic fine silica particles wherein the fine silicaparticles fulfill the following conditions (i) and (ii), (i) when anorganic compound which is liquid at room temperature and has adielectric constant of from 1 to 40 F/m and fine silane-surface-treatedsilica particles are mixed in a weight ratio of 5:1 and shaken, the finesilane-surface-treated silica particles disperse uniformly in theorganic compound; and (ii) the quantity of primary particles remainingas primary particles when methanol is evaporated under heating from adispersion prepared by dispersing the fine silane-surface-treated silicaparticles in methanol and thereafter holding the finesilane-surface-treated silica particles at a temperature of 100° C. for2 hours, is at least 20% based on the quantity of primary particlesoriginally present.
 2. The organic resin composition according to claim1, wherein the organic resin is a thermoplastic resin or a curableresin.
 3. The organic resin composition according to claim 1, whereinthe organic resin is selected from the group consisting of a polyolefin,a polyester, nylon 6 and nylon 6,6.
 4. The organic resin compositionaccording to claim 1, wherein the organic resin is selected from thegroup consisting of an epoxy resin, an unsaturated polyester resin, anepoxy acrylate resin, a urethane acrylate resin and mixtures thereof. 5.The organic resin composition according to claim 1, further comprisingone or more additive selected from the group consisting of anantioxidant, a UV light absorber, a processing aid, a colorant, anantistatic agent and a lubricant.
 6. The organic resin composition ofclaim 1, wherein the silane-surface-treated fine silica particles have aparticle diameter of from 0.05 to 1 μm.